This application claims the priority of German Application No. 10 2004 032 978.8 filed Jul. 8, 2004, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a flow structure for a turbocompressor. Preferred embodiments relate to a flow structure for a turbocompressor of a gas turbine, having at least one ring chamber which is arranged concentrically with respect to an axis of the turbocompressor in an area of free blade/vane ends of a rotor blade ring/vane ring and is adjacent radially to a main flow channel, whereby the ring chamber is bordered by a front upstream wall, a rear downstream wall and a wall extending essentially axially, whereby baffle elements are arranged in the ring chamber and whereby the ring chamber permits flow penetration in a circumferential direction in a front and/or rear area.
In addition, the invention relates to a turbocompressor and an aircraft engine and a stationary gas turbine.
Flow structures, i.e., circulation structures for turbocompressors are known in the form of so-called casing treatments and hub treatments. The primary function of casing treatments and hub treatments is to increase the aerodynamically stable operating range of a compressor by optimizing the surge limit interval. An optimized surge limit interval permits higher compressor pressures and thus a higher compressor load. The disturbances responsible for local flow breakaway and ultimately for pumping of the compressor occur on the casing ends of the rotor blades of one or more compressor stages and/or on the hub ends, which are on the inside radially, of the guide vanes, because the aerodynamic load in the compressor is greatest in these ranges. In the area of the blade/vane ends, the flow is stabilized by flow structures, i.e., circulation structures. Such circulation structures allow axial flow as well as flow penetration in the circumferential direction. Flow structures in the area of the casing ends of the rotor blades are referred to as “casing treatments”, while flow structures in the area of the hub ends of the guide vanes are referred to as “hub treatments”.
German Patent DE 33 22 295 C3 (corresponding U.S. Pat. No. 4,871,294) discloses an axial fan having a circulation structure. The axial fan according to this German Patent DE 33 22 295 C3 includes a ring chamber arranged concentrically with an axis of the axial fan in the area of free ends of a rotor blade ring, with the ring chamber being connected radially to a main flow channel. Baffle elements are fixedly arranged in the ring chamber. The circulation structure according to this state of the art permits flow axially and circumferentially. Characteristic of this type of circulation structures is a closed ring, which is flush with the contour of the main flow channel and separates the rear admission area of the circulation structure from the forward exit area of same and forms a smooth closed surface area.
U.S. Pat. No. 5,282,718 discloses a casing treatment having baffles arranged in a ring chamber. Again in this casing treatment, the admission area and the exit area of the circulation structure are separated by a solid closed ring, which is smooth in the direction of the vanes and blades. Such rings in the area of the vanes and blades must be provided with a strip coating or intake coating for the case of contact with the tips of the vanes and blades.
Another casing treatment is known from U.S. Pat. No. 5,137,419. Axial grooves and/or axially inclined grooves are provided with the circulation structure disclosed in that patent for improving the surge limit interval of a compressor in an axial design. However, with the circulation structure disclosed there, flow penetration in the circumferential direction is not possible.
Other circulation structures for turbocompressors are known from U.S. Pat. No. 4,511,308 and German Patent DE 35 39 604 C1 (corresponding U.S. Pat. No. 4,673,331).
In addition, it is already known in the state of the art that in the compressor area between neighboring vane rings and rotor blade rings, air may be branched off through openings in the compressor casing—so-called bleed slots—and this air is used, e.g., as compartment air or as cooling air for the turbine. However, this has a negative influence on the flow conditions prevailing at the downstream rotor blade grid in the sense of a reduction in the surge limit interval.
Against this background, the present invention is based on the problem of creating a novel flow structure for a turbocompressor which will permit in particular branching off of compressor air without any disadvantage from an aerodynamic standpoint.
This problem is solved by providing a flow structure for a turbocompressor of a gas turbine, having at least one ring chamber which is arranged concentrically with respect to an axis of the turbocompressor in an area of free blade/vane ends of a rotor blade ring/vane ring and is adjacent radially to a main flow channel, whereby the ring chamber is bordered by a front upstream wall, a rear downstream wall and a wall extending essentially axially, whereby baffle elements are arranged in the ring chamber and whereby the ring chamber permits flow penetration in a circumferential direction in a front and/or rear area, wherein, in the area of at least one of the walls, at least one opening is provided which permits flow penetration out of the ring chamber, and wherein there is at least one compressor chamber to receive this emerging flow.
According to this invention, at least one opening is provided in the area of at least one of the walls, permitting flow penetration out of the ring chamber, at least one compressor chamber being provided to accommodate the outgoing air.
The inventive flow structure acts at least partially as a casing treatment and/or a hub treatment with all the advantages in this regard and permits air to be branched off in an aerodynamically optimized manner. The present invention thus permits air circulation on the one hand while on the other hand also allowing air to be branched off. If no air is branched off, the air circulation acts exclusively as a casing treatment and/or hub treatment.
According to an advantageous embodiment of the invention, the baffle elements on the one hand border flow channels running primarily in the axial direction and on the other hand border at least one flow channel running in the circumferential direction, the opening or each opening being arranged on an upstream end of the flow channels running in the axial direction.
Preferably a medium, namely air, which flows into the compressor chamber through the flow channels running in the axial direction and through the opening or each opening, can be removed from the compressor chamber through an outlet opening.
The inventive flow structure is advantageously incorporated in turbocompressors for aircraft engines and stationary gas turbine engines.
Preferred embodiments of the present invention are derived from the dependent claims and the description below.
Exemplary embodiments of this invention will now be explained in greater detail on the basis of the drawing without being limited to that.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.